1. Field of the Invention
The present invention relates to apparatus for coupling an endoscope to a camera head. More particularly, this invention pertains to an endoscopic adapter that includes an improved arrangement for coupling an endoscope to a video camera head that prevents fogging of optical elements during use.
2. Description of the Prior Art
The field of video endoscopy to which the present invention generally relates includes medical, diagnostic and therapeutic disciplines that utilize endoscopes to penetrate and view internal body cavities and organs with minimal intrusion and surgical procedures. Conventional endoscopes can generally be categorized as rigid or flexible and include, for example, the laparoscope, cystoscope, arthroscope, ureterscope, bronchoscope, and colonscope.
Video endoscopy has greatly enhanced the utility of endoscopic procedures. This technological advance requires apparatus for coupling the endoscope to the video camera head. Various couplers or endoscopic adapters generally include both real image forming optics and focusing apparatus mounted within a sleeve. Exemplary couplers and adapters are described in U.S. Pat. Nos. 4,076,018 of Heckele; No. 4,279,246 of Chikama; No. 4,344,092 of Miller; No. 4,413,278 of Feinbloom; No. 4,414,576 of Randmae; No. 4,439,030 of Veda; No. 4,621,618 of Omagari; and 4,639,772 of Sluyter, et al.; and Japanese Patent No. 58-21134 of Nishigaki.
Before use, the complete endoscopic system, including endoscope, adapter and video camera head must be disinfected by soaking or immersion in an appropriate solution, followed by rinsing in sterile water, drying and assembly. However, the viewing clarity of the adapter can often be hampered by the unavoidable trapping of residual liquid particles inside the various chambers formed between the conventional adapter and endoscope, as well as those between the adapter and the video camera head.
The endoscopic system is, therefore, vulnerable to liquid condensation at the adapter's optical surfaces. Condensation of the particles, which are heated by the heat emitted by the illumination source, generally occurs at the relatively cool front window of the optical adapter which offers a lower moisture-pressure gradient than the surrounding metal surfaces. The resulting reduction in clarity can significantly hinder the physician's diagnostic ability and his ability to perform surgical procedures.
While various techniques and couplers have been employed to minimize the condensation of residual fluid on the viewing optics, none has proven to be entirely satisfactory. One such coupler is described in U.S. Pat. No. 4,611,888 to Prenovitz, et al. While providing a compact coupler, this device suffers from drawbacks that render it less than desirable for modern applications. The Prenovitz et al. apparatus includes front and rear sections that are rotatable relative to one another to cause similar rotation of the endoscope relative to the camera head. The device further includes sealing means for reducing fogging.
The Prenovitz et al. coupler is, however, unsuitable for arthroscopic procedures that require use of multiple, interchangeable endoscopes since it requires soaking of the complete endoscopic system as a unit for disinfection. In fact, disconnection during the surgery can expose the image forming optics of the endoscopic system to contamination by fluids surrounding the surgical wound.
U.S. Pat. No. 4,807,594 of Chatenever teaches an endoscopic system that includes a "glass-on-glass" arrangement for maintaining optical clarity despite the presence of trapped liquid particles. The device of that patent essentially comprises a mechanism for creating a glass-on-glass interface between the endoscope and the adapter by the intimate contact between optical surfaces that does not permit intrusion of liquid particles therebetween. A glass-on-glass structure is achieved by removing the eyepiece of a conventional endoscope and replacing it with a so-called ocular adapter that comprises a tube-like structure with an optical window that engages the proximal end of the endoscope. The window is aligned axially with the optics of the endoscope and the camera head. It protrudes slightly from the back wall of the ocular adapter toward an opposed window in the wall of the endoscope engageable portion of the adapter.
While providing an advantageous arrangement that is particularly useful for situations or procedures requiring more than one interchangeable endoscope, the glass-on-glass structure suffers numerous drawbacks. Particular care must be take to avoid scratching of the contacting optical windows. This requires, in part, a relatively-complex mechanical arrangement for moving the optical adapter into engagement with the endoscope engageable portion. Such a mechanism is required to control the purely axial interengagement of the two windows to avoid the potential scratching that can result from rotational motion between contacting windows. Further, the windows of the glass-on-glass device are necessarily formed of very hard, scratch-resistant (and expensive) materials such as sapphire. Finally, as it is often required to rotate the axis of the endoscope with respect to that of the camera head, the adapter-to-camera head mounting must permit rotation as rotation cannot occur between the endoscope and the adapter for the reasons discussed above.